The third international Ornithological Congress, held in Paris in 1900, decided that the Governments of the various European States should be called upon to have the food of birds made the object of special investigations, and to report the result, within a space of five years. When the fourth International Congress met, however, only Hungary and Belgium were able to report on the subject. The publications of the Hungarian Ornithological Centre are founded upon the collection of data, divided into two main groups:--1. The Migration data, so-called historical, up to 1891, and again from that to the present day. 2. Foreign data, partly taken from literature, and Special data relating to one species, from the whole area of its habitation--the Cuckoo for instance. The investigation of the economic rôle played by the Rook (Corvus frugilegus L.), which English landowners and farmers are beginning to feel is a matter of great importance, was begun by the Central Bureau in 1893; it is still going on. According to the results hitherto attained, this bird does more good by destroying insects, and in particular the larvæ of insects living underground, than it does harm to the crops. It is our endeavour in this little volume which we now offer to English readers, to give a faithful presentment of the good and the harm that the birds are known to do, from the agriculturist’s standpoint. But in this all depends on the attitude which the gardener and the farmer adopt towards the birds. By throwing a single stone a lad can scare away a whole flock of rooks; and when these birds alight on a field where they do harm to grain, a man must not grudge a little labour in keeping them off; considering that the same bird that works harm at one season, will be a valuable ally at another, as well as a source of pleasure and interest. The rook, the crow, and even the mischievous magpie, follow the plough as it turns up the brown furrows, with sharp eyes spying worms, larvæ and cockchafer grubs. Nothing escapes the attention of the bird. He picks here and there, and fills his crop with the worst enemies of the tiller of the fields--the various forms of insect life that lie dormant in the earth until the time arrives for each one to come forth and fulfil its life’s mission--much of which means injury to the fruit of man’s labour. Starlings rise in flocks--a perfect cloud of them--to disperse, and again to assemble before settling on the pastures, where they will be busy all the day, for that part of the year when man needs their services most.